STIs: Causes, Signs and Symptoms

Clinical safety and confidentiality notice: This is an educational guide for emergency-medicine students. A genital symptom is not a diagnosis, and many STIs are asymptomatic. Use confidential, non-judgemental history taking, the current Uganda Clinical Guidelines, appropriate laboratory testing and partner services. Urgent referral is required for shock, severe pelvic/testicular pain, pregnancy complications, sepsis, acute urinary retention, neurological illness or suspected sexual violence.

Sexually transmitted infections (STIs) are infections transmitted predominantly through sexual contact, including vaginal, anal, oral and genital skin-to-skin contact. Some also spread through blood, shared injecting equipment, pregnancy, childbirth or breastfeeding. The supplied 48-slide presentation covers common bacterial, viral and protozoal infections, risk factors, symptoms, testing, treatment principles and prevention; this post expands those points into a complete clinical framework.

Learning objectives

Classify common STIs by organism and transmission route.
Explain why many infected people have no symptoms and why screening matters.
Describe the typical symptoms and signs of chlamydia, gonorrhoea, syphilis, trichomoniasis, herpes, HPV, HIV, hepatitis B/C and other common infections.
Take a respectful sexual history, examine safely and select appropriate tests.
Recognise emergencies, pregnancy implications, partner-management needs and when syndromic care is appropriate.

1. Important terminology

Term	Meaning
STI	Infection acquired or transmitted through sexual contact; a person may have no symptoms.
STD	Older term implying disease/symptoms. STI is preferred because infection may be silent.
Index patient	The person presenting for evaluation; avoid language that implies blame.
Partner services	Confidential support for notifying, testing and treating sexual partners while protecting safety and privacy.
Incubation period	Time from exposure to first symptoms; differs by organism and may be followed by a longer window before tests become positive.
Window period	Time after infection during which a test may be negative despite infection; repeat testing may be needed.
Syndromic management	Treatment based on a defined symptom/sign cluster when laboratory confirmation is unavailable or delayed.
Asymptomatic infection	Infection without noticeable symptoms; still transmissible and capable of complications.

2. Classification of STIs

Group	Examples	General clinical principle
Bacterial	Chlamydia trachomatis, Neisseria gonorrhoeae, Treponema pallidum (syphilis), chancroid (Haemophilus ducreyi), donovanosis, Mycoplasma genitalium.	Many are curable with antibiotics, but resistance, reinfection and untreated complications are important.
Viral	HIV, herpes simplex (HSV-1/2), human papillomavirus (HPV), hepatitis B, hepatitis C, mpox and molluscum contagiosum.	Some are chronic or latent; antivirals, vaccination, monitoring and prevention reduce transmission and complications.
Protozoal/fungal/ectoparasitic	Trichomonas vaginalis, Candida species, pubic lice and scabies.	Some are sexually associated but not exclusively sexually transmitted; confirm the cause rather than treating every discharge as an STI.

3. How transmission occurs

Vaginal, anal or oral sex without an effective barrier; ejaculation is not required.
Direct skin-to-skin contact with infected lesions (HSV, HPV, syphilis, mpox) even without penetration.
Blood exposure, shared needles or unsafe medical equipment (HIV, hepatitis B/C).
Vertical transmission during pregnancy, birth or breastfeeding depending on the infection (HIV, syphilis, hepatitis B, gonorrhoea, chlamydia, HSV).
Autoinoculation from one infected site to another by touching/scratching in some infections.
STIs are not usually spread by toilet seats, casual handshakes, ordinary hugging, sharing plates or routine household contact. Avoid reinforcing myths that increase stigma.

4. Risk factors and vulnerability

New or multiple sexual partners, a partner with other partners, inconsistent/incorrect condom use or sex under the influence of alcohol/drugs.
Previous STI or HIV, untreated partner, sexual violence, transactional/coerced sex and inability to negotiate condoms.
Adolescence/young adulthood, mobility, displacement, incarceration, sex work, men who have sex with men, transgender people and other populations facing barriers to care.
Not vaccinated against HPV or hepatitis B, sharing injecting equipment, unsafe blood exposure or occupational needle injury.
Biological vulnerability: cervical ectopy in adolescents, mucosal trauma, pregnancy, immunosuppression and untreated genital inflammation.

5. Why symptoms may be absent

Chlamydia, gonorrhoea, HPV, HIV, hepatitis B/C, syphilis and trichomoniasis may be asymptomatic or produce symptoms that are mild, intermittent or mistaken for another condition. A person may transmit infection while feeling well. Screening, partner testing, pregnancy screening and risk-based retesting are therefore central to prevention. A normal-looking genital examination does not exclude infection.

6. Clinical manifestations by infection

6.1 Chlamydia

Chlamydia trachomatis is an intracellular bacterium affecting the urethra, cervix, rectum, pharynx or conjunctiva.

Often asymptomatic: particularly in women and rectal/pharyngeal infection.
Urethritis: dysuria, scant mucoid/mucopurulent discharge, urethral irritation, testicular pain or epididymitis.
Cervicitis: increased discharge, post-coital/intermenstrual bleeding, pelvic discomfort or dyspareunia.
Rectal infection: anorectal pain, discharge, bleeding, pruritus, tenesmus or painful defecation.
Complications: pelvic inflammatory disease (PID), infertility, ectopic pregnancy, chronic pelvic pain, epididymo-orchitis and neonatal conjunctivitis/pneumonia.

6.2 Gonorrhoea

Neisseria gonorrhoeae commonly infects the urethra, cervix, rectum, pharynx or conjunctiva and may coexist with chlamydia.

Men: abrupt dysuria, thick purulent urethral discharge, meatal inflammation, epididymitis or testicular pain.
Women: often asymptomatic; mucopurulent cervical discharge, dysuria, intermenstrual/post-coital bleeding, pelvic pain or dyspareunia.
Rectal/pharyngeal: discharge, pain, bleeding, tenesmus or sore throat; pharyngeal disease may be silent.
Disseminated infection: fever, migratory polyarthralgia, tenosynovitis, pustular skin lesions, septic arthritis or rarely meningitis/endocarditis.
Newborn risk: severe ophthalmia neonatorum and systemic infection.

6.3 Syphilis

Treponema pallidum is transmitted by contact with infectious lesions and can cross the placenta.

Stage	Typical findings
Primary	Single or multiple painless, clean-based indurated chancre at genital, anal, oral or other inoculation site; non-tender regional lymphadenopathy. The lesion may be hidden internally or heal spontaneously.
Secondary	Fever, malaise, sore throat, generalised lymphadenopathy, diffuse non-itchy rash including palms/soles, mucous patches, condylomata lata, alopecia and weight loss.
Latent	No clinical signs; infection detected by serology. Early latent infection remains more transmissible.
Tertiary	Years later: gummas, aortitis/cardiovascular disease, ocular disease, neurosyphilis, sensory ataxia and neuropsychiatric change. Neurosyphilis can occur at any stage.
Congenital	Miscarriage, stillbirth, hydrops, prematurity, snuffles, rash, hepatosplenomegaly, bone disease, deafness or neurological injury.

6.4 Trichomoniasis

Trichomonas vaginalis is a motile protozoan affecting the vagina, urethra and prostate.

Women: vulvovaginal itching/burning, dysuria, dyspareunia, yellow-green or frothy offensive discharge, vulval erythema and a punctate “strawberry cervix”.
Men: commonly asymptomatic; dysuria, urethral irritation or scant discharge may occur.
Complications: increased HIV acquisition/transmission risk, pregnancy complications and recurrent infection if partners are untreated.

6.5 Genital herpes

HSV-1 or HSV-2 establishes lifelong latency with episodic reactivation.

Prodrome: local tingling, burning, pain or itching.
Clusters of painful vesicles rupture into shallow ulcers on the vulva, penis, scrotum, perineum, buttocks, anus, vagina or cervix.
Primary episodes may cause fever, headache, myalgia, dysuria, painful urination due to external lesions and tender inguinal nodes.
Recurrences are usually shorter and milder; triggers include stress, illness, menstruation, fatigue and immunosuppression.
Pregnancy concern: new infection near delivery can cause severe neonatal herpes; urgently involve obstetric care.

6.6 Human papillomavirus (HPV)

Often asymptomatic; low-risk types 6/11 cause anogenital warts, while persistent high-risk types can cause cervical, anal, penile, vulval, vaginal and oropharyngeal precancer/cancer.
Warts may be flesh-coloured, pink, white or pigmented; single, multiple, papillary or cauliflower-like; they may itch, bleed or obstruct the urethra/anus.
Visible warts do not identify the HPV type or cancer risk. Cervical screening remains important.

6.7 HIV infection

Acute infection, usually 2–4 weeks after exposure, may cause fever, sore throat, rash, lymphadenopathy, myalgia, diarrhoea, headache or oral/genital ulcers—or no symptoms.
Clinical latency can last years. Progressive untreated disease may cause weight loss, persistent fever/diarrhoea, recurrent infections, oral thrush, tuberculosis, shingles, neurological disease and malignancy.
Testing is the only way to know status. Early ART improves health and prevents sexual transmission when viral load is suppressed; it does not prevent other STIs.

6.8 Hepatitis B and C

Often asymptomatic; acute hepatitis may cause fatigue, nausea, anorexia, right-upper-quadrant discomfort, dark urine, pale stool and jaundice.
Chronic infection can cause cirrhosis, liver failure and hepatocellular carcinoma. Hepatitis B is vaccine-preventable; hepatitis C has no vaccine but is curable with direct-acting antivirals.
Blood exposure and vertical transmission are important; assess pregnancy/newborn prevention pathways.

6.9 Molluscum contagiosum, mpox and ectoparasites

Molluscum: pearly, umbilicated papules; sexual transmission is possible in adults but lesions may also spread through nonsexual skin contact.
Mpox: fever, lymphadenopathy and deep-seated painful or itchy lesions that may involve genital/perianal skin; urgent public-health guidance is required for suspected cases.
Pubic lice/scabies: intense itching, excoriations, nits or burrows; treat the person, close contacts and clothing/bedding according to local protocol.

7. Symptoms grouped by syndrome

Syndrome	Possible causes	Important questions/signs
Urethral discharge/dysuria	Gonorrhoea, chlamydia, trichomoniasis, Mycoplasma genitalium, UTI, trauma or irritant.	Onset, colour/amount, dysuria, testicular pain, recent partners, antibiotics, fever and sexual sites.
Vaginal discharge/itch	Trichomoniasis, candidiasis, bacterial vaginosis, cervicitis or retained foreign body.	Odour, colour, froth, pelvic pain, fever, post-coital bleeding, pregnancy and vulval lesions.
Genital ulcer/blister	HSV, syphilis, chancroid, LGV, trauma, fixed-drug eruption, aphthous disease or malignancy.	Pain, number, induration, vesicles, necrosis, inguinal nodes, duration and systemic symptoms.
Lower abdominal pain	PID, ectopic pregnancy, appendicitis, UTI, ovarian torsion or endometriosis.	Pregnancy possibility, fever, cervical motion/adnexal tenderness, bleeding, vomiting and shock.
Scrotal pain/swelling	Epididymo-orchitis, torsion, hernia, trauma or tumour.	Sudden onset/torsion signs, fever, discharge, urinary symptoms and testicular position.
Anal/throat symptoms	Rectal/pharyngeal gonorrhoea/chlamydia, HSV, syphilis, mpox, fissure or non-STI disease.	Ask about exposure site; examine and test the anatomical site, not urine alone.

8. Clinical assessment

8.1 A respectful sexual history

Use the five Ps: partners, practices, protection, past STIs/pregnancy and prevention of pregnancy.
Ask gender-neutral, open questions: “What parts of the body were involved?” and “What protection was used?” rather than assuming heterosexual vaginal sex.
Clarify date of last exposure, number/newness of partners, condom use, oral/anal/vaginal sites, sexual violence/coercion, symptoms in partners and previous treatment.
Ask pregnancy possibility, contraception, HIV/PrEP/PEP, vaccines, allergies, medication and antibiotic use.
Screen for safety, intimate-partner violence and ability to notify partners. Interview adolescents privately according to law and safeguarding policy.

8.2 Examination

Explain, obtain consent and offer a chaperone; expose only relevant areas.
General: fever, rash, oral lesions, lymphadenopathy, jaundice, weight loss, pallor and sepsis.
Genital: discharge, ulcers, vesicles, warts, inflammation, inguinal nodes, testicular/epididymal tenderness or pelvic tenderness.
Anal/oral examination when symptoms or exposure warrant it; use appropriate lighting and PPE.
In women with lower abdominal pain, assess pregnancy, cervical motion/adnexal tenderness and peritonism; avoid delaying ectopic-pregnancy care.

9. Diagnostic investigations

Test/approach	Use	Limitations/interpretation
NAAT/PCR	Chlamydia, gonorrhoea, trichomonas and selected sites; urine, vaginal/cervical, rectal or pharyngeal specimens.	Collect from the exposed anatomical site; a negative urine test does not exclude rectal/pharyngeal infection.
Microscopy	Wet mount for motile trichomonads, yeast/clue cells; Gram stain in selected settings.	Sensitivity depends on timing, specimen and operator; negative microscopy may need NAAT.
Culture and antimicrobial susceptibility	Gonorrhoea where resistance surveillance or treatment failure is suspected.	Correct swab/transport and pre-treatment sample are important.
Syphilis serology	RPR/VDRL plus treponemal confirmation or approved rapid algorithm.	Early infection may be seronegative; titres help monitor response but do not alone diagnose stage.
HIV testing	National serial algorithm with consent, counselling and linkage.	Consider window period and repeat after recent exposure; never disclose without permission.
Hepatitis B/C testing	HBsAg and appropriate confirmatory/staging tests; HCV antibody with RNA confirmation where available.	Interpret in pregnancy, liver disease and recent exposure context.
Pregnancy test/ultrasound	For lower abdominal pain, bleeding, PID treatment choices or sexual assault.	Rule out ectopic pregnancy and protect the fetus when selecting medicines.

10. When to refer urgently

Shock, sepsis, high fever or rapidly spreading infection.
Severe lower-abdominal pain, guarding, ectopic-pregnancy possibility or tubo-ovarian abscess.
Acute severe unilateral testicular pain/swelling (testicular torsion until excluded).
Disseminated gonococcal infection, meningitis, endocarditis or severe mpox.
New genital herpes or syphilis in pregnancy, suspected congenital infection or neonatal eye discharge.
Sexual assault with serious injury, strangulation, suicidal thoughts or immediate safety threat.
Urinary retention, extensive necrotic ulcers, rapidly enlarging warts or suspected malignancy.

11. General treatment principles (before the dedicated management posts)

Test and treat according to Uganda Clinical Guidelines and current antimicrobial-resistance patterns; do not copy an outdated slide dose blindly.
Where syndromic management is indicated, treat all likely causes at the first visit, provide a laboratory sample before antibiotics when feasible and arrange review.
Complete the prescribed course, check allergies, pregnancy/breastfeeding, renal/hepatic disease and drug interactions.
Abstain from sexual contact until the patient and relevant partners have completed treatment and the recommended waiting period has passed; use condoms thereafter.
Offer HIV, syphilis, hepatitis and pregnancy testing as appropriate; treat/notify partners confidentially and safely.
Retest for reinfection at the interval recommended by the pathogen/national guideline. Persistent symptoms require re-examination, adherence/resistance assessment and alternative diagnoses.

12. Prevention overview

Correct and consistent condoms/internal condoms and dental dams; lubricants reduce breakage.
Mutual testing and agreed safer-sex plans; reduce overlapping partnerships if desired, without moral judgement.
HPV and hepatitis B vaccination according to Uganda schedule.
HIV PrEP for people with ongoing risk and PEP after significant exposure; condoms still prevent other STIs.
Routine antenatal screening, safe blood/injections, sterile equipment and prevention of mother-to-child transmission.
Prompt treatment, partner services, screening of asymptomatic contacts and stigma-free access to care.

13. Worked cases

Case 1: asymptomatic partner of chlamydia

A 20-year-old has no symptoms but her partner tested positive. Do not reassure based on examination alone. Take an exposure history, test the relevant sites, assess pregnancy and HIV/syphilis risk, treat according to the current guideline and arrange partner/reinfection follow-up.

Case 2: painful genital blisters in pregnancy

Clusters of painful vesicles with dysuria suggest genital herpes. Confirm where available, assess gestation and systemic illness, start pregnancy-compatible antiviral management under obstetric guidance and plan delivery/newborn protection. Review urgently if urinary retention or severe disease develops.

Case 3: dysuria plus purulent discharge

Consider gonorrhoea and chlamydia, obtain a urethral/urine NAAT or culture before treatment when possible, assess testicular pain and disseminated symptoms, treat per Uganda protocol and provide partner management, abstinence and retesting advice.

Quick self-test

Why can a normal examination not exclude an STI?
What are the five Ps of a sexual history?
Name four infections that may be asymptomatic.
Which symptoms suggest disseminated gonococcal infection?
Why must rectal or pharyngeal exposure be tested at the exposed site?
List five situations requiring urgent referral.

Answers

Many STIs are asymptomatic, lesions may be internal/healed and examination sensitivity is limited.
Partners, practices, protection, past STIs/pregnancy and prevention of pregnancy.
Chlamydia, gonorrhoea, HPV, HIV, hepatitis B/C, syphilis and trichomoniasis are examples.
Fever, migratory polyarthralgia, tenosynovitis, pustular lesions, septic arthritis, meningitis or endocarditis.
Infection can be site-specific; urine testing may miss rectal/pharyngeal disease.
Shock/sepsis, severe pelvic pain/ectopic concern, acute testicular torsion, disseminated infection, pregnancy/neonatal risk, serious assault or urinary retention.

Further study and source integration

Take-home message: Treat the person, not the stigma or a single symptom. Ask respectfully, examine safely, test the exposed sites, consider asymptomatic infection, treat promptly using current Uganda guidance and connect every patient to prevention and partner services.

Doctors Revision

Causes, Signs and Symptoms of Sexually Transmitted Infections: Comprehensive Clinical Guide